Angle-Weighted Reverse Time Migration With Wavefield Decomposition Based on the Optical Flow Vector

Reverse time migration (RTM) is based on the two-way wave equation, so its imaging results obtained by conventional zero-lag cross-correlation imaging conditions contain a lot of low-wavenumber noises. So far, the wavefield decomposition method based on the Poynting vector has been developed to suppress these noises; however, this method also has some problems, such as unstable calculation of the Poynting vector, low accuracy of wavefield decomposition, and poor effect of large-angle migration artifacts suppression. This article introduces the optical flow vector method to RTM to realize high-precision wavefield decomposition for both the source and receiver wavefields and obtains four directions of wavefields: up-, down-, left-, and right-going. Then, the cross-correlation imaging sections of one-way propagation components of forward- and back-propagated wavefields are optimized and stacked. On this basis, the reflection angle of each imaging point is calculated based on the optical flow vector, and an attenuation factor related to the reflection angle is introduced as the weight to generate the optimal stack images. The tests of theoretical model and field marine seismic data illustrate that compared with the conventional RTM with wavefield decomposition based on the Poynting vector, the angle-weighted RTM with wavefield decomposition based on the optical flow vector proposed in this article can achieve wavefield decomposition for both the source and receiver wavefields and calculate the reflection angle of each imaging point more accurately and stably. Moreover, the proposed method adopts angle weighting processing, which can further eliminate large-angle migration artifacts and effectively improve the imaging accuracy of RTM.

A Theory for Electromagnetic Radiation and Coupling

A theory for analyzing the radiative and reactive electromagnetic energies of a radiator in vacuum is presented. In vacuum, the radiative electromagnetic energies will depart from their sources and travel to infinity, generating a power flux in the space. However, the reactive electromagnetic energies are bounded to their sources. They appear and disappear almost in the same time with their sources, and their fluctuation also causes a power flux in the space. In the proposed theory, the reactive electromagnetic energies of a radiator are defined by postulating that they have properties similar to the self-energies in the charged particle theory. More importantly, in addition to a main term of source-potential products, the reactive energies contain a special energy term which will last to exist a short time after the sources disappear. This oscillating energy is related to the electric displacement and the vector potential, and seems to be responsible for energy exchanging between the reactive energy and the radiative energy in the radiation process, performing like the Schott energy term. As the Poynting vector describes the total power flux density related to the total electromagnetic energy, it should include the contributions of the propagation of the radiative energies and the fluctuation of the reactive energies. The mutual electromagnetic couplings between two radiators are also defined in a similar way in which the vector potential plays a central role. The reactive electromagnetic energies can be evaluated with explicit expressions in time domain and frequency domain. The theory is verified with the Hertzian dipole and numerical examples.

A Theory for Electromagnetic Radiation and Coupling

A theory for analyzing the radiative and reactive electromagnetic energies of a radiator in vacuum is presented. In vacuum, the radiative electromagnetic energies will depart from their sources and travel to infinity, generating a power flux in the space. However, the reactive electromagnetic energies are bounded to their sources. They appear and disappear almost in the same time with their sources, and their fluctuation also causes a power flux in the space. In the proposed theory, the reactive electromagnetic energies of a radiator are defined by postulating that they have properties similar to the self-energies in the charged particle theory. More importantly, in addition to a main term of source-potential products, the reactive energies contain a special energy term which will last to exist a short time after the sources disappear. This oscillating energy is related to the electric displacement and the vector potential, and seems to be responsible for energy exchanging between the reactive energy and the radiative energy in the radiation process, performing like the Schott energy term. As the Poynting vector describes the total power flux density related to the total electromagnetic energy, it should include the contributions of the propagation of the radiative energies and the fluctuation of the reactive energies. The mutual electromagnetic couplings between two radiators are also defined in a similar way in which the vector potential plays a central role. The reactive electromagnetic energies can be evaluated with explicit expressions in time domain and frequency domain. The theory is verified with the Hertzian dipole and numerical examples.

A Theory for Electromagnetic Radiation and Coupling

A theory for analyzing the radiative and reactive electromagnetic energies of a radiator in vacuum is presented. In vacuum, the radiative electromagnetic energies will depart from their sources and travel to infinity, generating a power flux in the space. However, the reactive electromagnetic energies are bounded to their sources. They appear and disappear almost in the same time with their sources, and their fluctuation also causes a power flux in the space. In the proposed theory, the reactive electromagnetic energies of a radiator are defined by postulating that they have properties similar to the self-energies in the charged particle theory. More importantly, in addition to a main term of source-potential products, the reactive energies contain a special energy term which will last to exist a short time after the sources disappear. This oscillating energy is related to the electric displacement and the vector potential, and seems to be responsible for energy exchanging between the reactive energy and the radiative energy in the radiation process, performing like the Schott energy term. As the Poynting vector describes the total power flux density related to the total electromagnetic energy, it should include the contributions of the propagation of the radiative energies and the fluctuation of the reactive energies. The mutual electromagnetic couplings between two radiators are also defined in a similar way in which the vector potential plays a central role. The reactive electromagnetic energies can be evaluated with explicit expressions in time domain and frequency domain. The theory is verified with the Hertzian dipole and numerical examples.